Basic Differences Between AM and FM

We need to mention a couple of other things before we leave the discussion of how radio works.  We’ve talked about AM and FM radio, but we haven’t explained the real difference.

In fact, there is a lot of difference — and not just a difference in the station numbers on your radio dial.

The first type of radio service — the one we’ve been talking about in the last couple of modules — was AM radio.

The term modulation refers to how sound is encoded on a radio wave called a carrier wave; or, more accurately, how the sound affects the carrier wave so that the original sound can later be detected by a radio receiver.

In the top-left of this drawing the RF energy (carrier wave) is not modulated by any sound.  There would be silence on your radio receiver.

Sound transmitted by an AM radio station affects the carrier wave by changing the amplitude (height) of the carrier wave, as shown on the left.

Unfortunately, this type of modulation is subject to static interference from such things as household appliances — and especially from lightening storms.

AM also limits the loud-to-soft range of sounds that can be reproduced (called dynamic range) and the high-to-low sound frequency range (called frequency response, to be explained below).

FM radio, which came along in the 1930s, uses a different approach than AM. It’s virtually immune to any type of external interference, it has a greater dynamic range, and it can handle sounds of higher and lower frequencies. This is why music, with its much greater frequency range than the human voice, sounds better on FM radio.

Note on the left that when the carrier wave of FM radio is modulated with sound that the distance between the waves, or the frequency of the carrier wave, changes.

Thus, AM radio works by changing the amplitude of the carrier wave and FM radio works by changing the frequency of the carrier wave.

Frequency Response

Frequency relates to the basic pitch of a sound — how high or low it is. A frequency of 20 Hz would sound like an extremely low-pitched note on a pipe organ — almost a rumble.

At the other end of the scale, 20,000 Hz would be the highest pitched sound that can be imagined, even higher than the highest note on a violin or piccolo.

As we’ve noted, frequency is measured in Hertz (Hz) or cycles per second (CPS). A person with exceptionally good hearing will be able to hear sounds from 20-20,000 Hz.

Since both ends of the 20-20,000Hz range represent rather extreme limits, the more common range used for FM radio and TV is from 50 to 15,000 Hz. (A typical AM radio signal does not cover this entire range.)

Although the 50-15,000 Hz doesn’t quite cover the full range that can be heard by people with good hearing, it covers almost all naturally occurring sounds.  Note in the drawing above that the ear does not hear all frequencies of sound at the same loudness, but a good microphone does.

The sound level or amplitude of sound in radio and TV stations is monitored and adjusted with the help of a volume units meter (VU meter) meter. One model is shown on the left.  Audio levels must be carefully controlled in broadcasting to keep noise and distortion from reducing the quality of sound.

Radio, a potential medium for education

While admiring the growth of radio production and broadcast technology, Madhu Ranjan feels that it still continues to be an under-utilized technology in education. According to her, radio has enormous potential to improve distance education systems especially when integrated with other technologies such as television, mobile telephones, and the Internet.

Soon after its invention in the late 1890s, radio, due to its information and

entertainment value, vast reach, and immediacy, became the most popular means of mass communication around the world.

With the arrival of television, the birth of satellite broadcasting technology, and later the Internet, radio’s listener base began to erode and its importance diminished.  In the 1970s, however, radio (FM band) once again gained popularity, especially among young listeners.

Today, improved broadcasting quality, more innovative and entertaining content, and new technological developments in fields such as digital and satellite radio have made radio a resurgent medium, extremely popular in the fields of advertising and entertainment. Affordability, portability, and access indoors and outdoors give radio a clear edge over other media. Additionally, radio is increasingly becoming a more dynamic medium, as it is integrated into other new technologies such as television, mobile telephones, and the Internet.

This has opened up new opportunities for a variety of forms of delivery and access. For example, portable, low-cost FM transmitting stations have been developed and digital radio systems that transmit via satellite are being set up in many parts of the world. Internet streaming audio software technology now allows a global audience to listen to news from a distant country. In addition, the development of wind-up and solar radios utilizing inexpensive power sources allows radio to can cut across geographic, economic, and cultural boundaries.

However, radio still continues to be an under-utilized technology in education. This is somewhat surprising because, for a learner, radio is a simple, user friendly, accessible, and a well-established medium. From an educational provider’s point of view it is easy and inexpensive to set up, produce, and broadcast programs. Most nations currently have the engineering skills and broadcasting talent to apply this technology to education.

Today, many schools, colleges, universities, and other organizations use distance education systems. While developing a distance education system, factors such as cost effectiveness, efficiency, and the availability of appropriate communication technologies, as well as access and equity issues, particularly those related to gender, language, social status, and religion, are the most important considerations.

Other factors to consider relate to how distance learners can best use their higher order thinking skills and how they can cope with the limitations of time, age, gender, and language. Radio is able to address these issues while reaching a diverse group of learners and can be valuable in many different distance learning environments including schools, colleges and universities, businesses, and public sector organizations.

For distance education providers, radio is a cheaper alternative to other communication technology mediums. Producing interactive radio programs in distance education requires only low-priced equipment compared with other cutting-edge technologies. Educational institutions do not need to spend much money for establishing interactive radio studios in their organizations.

Learners are equally fortunate, because they do not have to buy or rent the costly and complex equipment required by TV and the Internet. There are no boundaries to broadcasting educational programs with interactive radio throughout the world and as long as learners have access to a very low-cost radio, they can listen to programs wherever they are; riding in their cars, traveling by bus or train, or working at home.

Moreover, interactive distance educational programs can be recorded for learners via inexpensive equipment, such as cassettes, CDs, or MP3 players. Educational radio helps provide equal access to knowledge for everyone by breaking digital walls around the world.

Interactive radio programs allow people with disabilities (with the exception of the hearing-impaired) to hear the voices of instructors, classmates, and experts, enhancing their ability to learn. While listening to interactive radio programs, learners have more time to construct knowledge.

Community radio is also an immensely powerful technology for the delivery of information with enormous global potential.  It is particularly powerful in providing access to information for marginalized populations, including women, minorities, and the poor, who often do not have access to more cutting edge technology. Radio can expand opportunities for the intended beneficiaries of development to participate in the in the development agenda, which can appropriately and adequately respond to their needs and aspirations.

Currently, the benefits of radio as a learning medium are overlooked. Conventional wisdom assumes that high-cost communication media ensure better interactive distance learning. Radio, however, when incorporated with interactive learning approaches, has enormous potential to improve distance education systems. In a very imaginatively designed program – funded by USAID and implemented by EDC – that makes the process of teaching-learning interesting and meaningful, radio lessons that introduce substantial interaction among students and teachers are improving classroom interaction in close to 300,000 government schools reaching over 25 million primary school students across several states in India.

Many interventions around the world are using radio innovatively; successfully enhancing the quality of teaching learning in traditional classroom settings, imparting health messages to communities; and providing useful information on agriculture to farmers.  Although it is not currently being exploited to its full potential, radio is a medium with tremendous potential, particularly for educational purposes. Get payday advance service for easy payment

How have radio and TV broadcasting been used in education?

Radio and television have been used widely as educational tools since the 1920s and the 1950s, respectively. There are three general approaches to the use of radio and TV broadcasting in education:

1. direct class teaching, where broadcast programming substitutes for teachers on a temporary basis;
2. school broadcasting, where broadcast programming provides complementary teaching and learning resources not otherwise available
3. general educational programming over community, national and international stations which provide general and informal educational opportunities

The most notable and best documented example of the direct class teaching approach is Interactive Radio Instruction (IRI).This consists of “ready-made 20-30 minute direct teaching and learning exercises to the classroom on a daily basis. The radio lessons, developed around specific learning objectives at particular levels of maths, science, health and languages in national curricula, are intended to improve the quality of classroom teaching and to act as a regular, structured aid to poorly trained classroom teachers in under-resourced schools.” IRI projects have been implemented in Latin America and Africa. In Asia, IRI was first implemented in Thailand in 1980; Indonesia, Pakistan, Bangladesh and Nepal rolled out their own IRI projects in the 1990s. What differentiates IRI from most other distance education programs is that its primary objective is to raise the quality of learning – and not merely to expand educational access – and it has had much success in both formal and non-formal settings. Extensive research around the world has shown that many IRI projects have had a positive impact on learning outcomes and on educational equity. And with its economies of scale, it has proven to be a cost-effective strategy relative to other interventions.

Mexico’s Telesecundaria is another notable example of direct class teaching, this time using broadcast television. The programme was launched in Mexico in 1968 as a cost-effective strategy for expanding lower secondary schooling in small and remote communities.Perraton describes the programme thus:

Centrally produced television programs are beamed via satellite throughout the country on a scheduled basis (8 am to 2 pm and 2 pm to 8 pm) to Telesecundaria schools, covering the same secondary curriculum as that offered in ordinary schools. Each hour focuses on a different subject area and typically follows the same routine – 15 minutes of television, then book-led and teacher-led activities. Students are exposed to a variety of teachers on television but have one home teacher at the school for all disciplines in each grade.

The design of the programme has undergone many changes through the years, shifting from a “talking heads” approach to more interactive and dynamic programming that “link[s] the community to the programme around the teaching method. The strategy meant combining community issues into the programs, offering children an integrated education, involving the community at large in the organization and management of the school and stimulating students to carry out community activities.” Assessments of Telesecundaria have been encouraging: drop out rates are slightly better than those of general secondary schools and significantly better than in technical schools. In Asia, the 44 radio and TV universities in China (including the China Central Radio and Television University), Universitas Terbuka in Indonesia, and Indira Ghandi National Open University have made extensive use of radio and television, both for direct class teaching and for school broadcasting, to reach more of their respective large populations. For these institutions, broadcasts are often accompanied by printed materials and audio cassettes.

Japan’s University of the Air was broadcasting 160 television and 160 radio courses in 2000. Each course consists of 15 45-minute lectures broadcast nationwide once a week for 15 weeks. Courses are aired over University-owned stations from 6 am to 12 noon. Students are also given supplemental print materials, face-to-face instruction, and online tutorials.

Often deployed with print materials, cassettes and CD-ROMS, school broadcasting, like direct class teaching, is geared to national curricula and developed for a range of subject areas. But unlike direct class instruction, school broadcasting is not intended to substitute for the teacher but merely as an enrichment of traditional classroom instruction. School broadcasting is more flexible than IRI since teachers decide how they will integrate the broadcast materials into their classes. Large broadcasting corporations that provide school broadcasts include the British Broadcasting Corporation Education Radio TV in the United Kingdom and the NHK Japanese Broadcasting Station. In developing countries, school broadcasts are often a result of a partnership between the Ministry of Education and the Ministry of Information.

General educational programming consists of a broad range of programme types – news programs, documentary programs, quiz shows, educational cartoons, etc. – that afford non-formal educational opportunities for all types of learners. In a sense, any radio or TV programming with informational and educational value can be considered under this type. Some notable examples that have a global reach are the United States-based television show Sesame Street, the all-information television channels National Geographic and Discovery, and the radio programme Voice of America.The Farm Radio Forum, which began in Canada in the 1940s and which has since served as a model for radio discussion programs worldwide, is another example of non-formal educational programming. It shows that you can also learn from lecturers with or without ID lanyards that represents certain University or college.

Radio in Education

From the start, in both Europe and America radio was greeted with hopes for its pedagogical value. Radio had the power to bring the world to the classroom, and programs could be presented as textbooks of the air.

In America, commercial and educational stations received licenses starting in the 1920s to produce classroom broadcasting, and eventually national networks also provided educational programs. Even though most programs were in line with traditional school subjects, some attempted to connect this content with progressive ideas about education and democracy. Radio allowed children and teachers to engage in the production of programs, preparing talks on, for example, automobiles, farming, and science. Together with the fact that parents supplied schools with radio receivers, this reflected a certain degree of local engagement in the implementation of radio in schools. However, this is not a perspective that has been emphasized in research. On the contrary, the organization of radio in education in America has been described as top down implementation. One example of this was the fact that superintendents, not teachers, were supposed to answer questionnaires, indicating that teachers were not included in the implementation process.

In contrast to America, broadcast systems in Europe were organized as nationwide networks that could be used for the inculcation of national values and virtues. Issues regarding educational as well as social and cultural policy were included in the broadcast organizations–in other words, they became part of welfare policy. In this context, children became a special interest.

In Scandinavian countries and Britain, special departments for educational programs were organized in the late 1920s or early 1930s. In general these programs were in line with the overall curriculum. However, a study on the use of radio in classrooms in Sweden reveals that there were contrasts between the content of ordinary schoolbooks and the content of radio programs. Radio programs emphasized contemporary progressive ideas on education and progressive political notions that were not represented in schoolbooks at that time. Citizenship, a new subject, was also given a particularly radical formulation in the school programs. This meant that children who listened to educational programs on the radio, discussed the programs, and did assignments on them, encountered views of society that differed from prevailing traditional middle-class representations. Reoccurring subjects included the everyday lives of the working or lower-middle classes as well as the need for health reform and an expanded welfare system.

In Sweden, educational broadcasts addressed children not only as future citizens but also as active contemporary citizens. Children were included in the actual broadcasts, where they were displayed, with references to famous scientific explorers like Sven Hedin, as competent explorers of their own society. Further, these children were enlisted to represent various parts of society in accordance with notions of society proposed by progressive policymakers. Each pupil was supposed to have his or her own program sheet where each program was presented in texts and pictures. The notion was that the material should help children to create “listening pictures” (hörbilder) when listening to programs. This practice was implemented out of a strong belief that a will to change the way people thought had to start with strategies that changed the way they talked.

In contrast to America, and in spite of the centralized organization, in Sweden teachers were included in the implementation of radio in education. They participated continually in surveys where they reported their own and the pupils’ responses to programs. Active teachers were invited to annual conferences about the use of radio in classrooms. It was argued by teachers and by the organizers of school broadcasts that elementary schoolteachers were more competent than academics and experts in communicating with pupils and therefore were invited to produce programs.

In Britain, educational radio programs were regarded as an important way to influence individual children and adolescents when they had problems or needed guidance in societal matters. Radio was also used to inculcate new notions of citizenship.

Further Research

Studies of children’s radio programs, particularly educational programs, offers an area of research that brings new perspectives to social, cultural, and political history. Such research also expands investigations of children’s increased visibility and status as a special group in society, for instance as reflected in the UN CONVENTION ON THE RIGHTS OF THE CHILD (1989). Children’s programs provide material for inquiries into children’s place in society as well as representations of childhood from a historical perspective, particularly during the period from 1920 to 1960, when radio was regarded as the major electronic medium in society. It is also a field well attuned to further developments of theoretical and methodological issues. In addition to actual programs, manuscripts, program sheets, and other documents concerning children’s broadcasts, a number of studies measure children’s reading and comprehension skills in relation to radio. Such materials could be used to investigate the systems of knowledge and meaning that have affected the child in different decades of the twentieth century.